The present invention relates to antennas, antenna arrays and the like, and more particularly to a low-bit phase shifter phased array antenna including a phase shifter controller and algorithm adapted for steering or pointing a beam from the array in a desired direction.
Currently, antenna arrays with densely placed elements, for example arrays with spacing approximately 0.1 wavelengths between elements, treat the array as analogous to a phase grating. In this approach phase shifter settings are determined by an optical grating equation for each row of the array with a phase modulation period, Λ, given by equation 1:
                    Λ        =                  λ                      n            -                          sin              ⁢                                                          ⁢                              (                                  θ                  o                                )                                                                        (        1        )            
Where λ is the frequency wavelength, n is the square of the relative dielectric constant of the feeding line (in an optical implementation, this would be the index of refraction of the lens material), and θo is the desired scan angle. The phase shifter settings are then set to achieve a square-wave phase modulation with the computed period. In other words, a number of phase shifters that are contained in the distance Λ/2 would be set to 0 degree phase. The next set of phase shifters in distance Λ/2 would be set to 180 degree phase. The result is a periodic phase modulation with period Λ. A two dimensional scan is then realized by applying the phase modulation to the rows (instead of elements in a row) to steer the beam in the other dimension. The resulting phase modulation is then a summation of the row phase grating and the orthogonal modulation applied to each row. However, this periodic phase modulation gives inferior performance because of high side lobes in the radiation pattern and other anomalies due to the accumulation of residual errors. An additional drawback to this approach is that the beam positions are discrete depending on the ability of the elements to achieve the period Λ.